<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>px-em-rem</title>
  <style>
    /* html {
      font-size: 16px;
    } */
  </style>
</head>
<body>
  <span style="font-size: 1em;">测试文字1em</span>
  <br />
  <span style="font-size: 1rem;">测试文字1rem</span>
  <br />
  <input type="color">
</body>
</html>